Motor stop control method and motor stop control apparatus

Abstract

According to an aspect of the invention, a motor stop control method of a motor stop control apparatus which includes an arithmetic control unit and a detection unit. The arithmetic control unit has a stop start position at which a stop control is started from a position which is a predetermined angle before a target position at which a motor stops. The arithmetic control unit calculates a rotational speed of the motor at the stop start position on the basis of a detection value of the detection unit, and a stop time at which the rotational speed of the motor reaches zero from the stop start position on the basis of a deceleration line indicating a change in the rotational speed of the motor, the rotational speed of the motor, and the predetermined angle.

What is claimed is: 
     
       1. A motor stop control method of a motor stop control apparatus including an arithmetic controller that controls a motor and a detector that detects a rotational state of the motor, the arithmetic controller having a control cycle which is a sampling interval used in detecting the rotational state of the motor at regular intervals and a stop start position at which a stop control is started from a position which is a predetermined angle before a target position at which the motor stops, the motor stop control method comprising:
 a rotational speed calculation step in which a rotational speed of the motor at the stop start position is calculated from a detection value detected by the detector; 
 a stop time calculation step in which the arithmetic controller calculates a stop time until the rotational speed of the motor reaches zero from the stop start position, on the basis of a deceleration line indicating a change in the rotational speed of the motor, the rotational speed, and the predetermined angle; 
 a rotational speed target value calculation step in which the arithmetic controller calculates a rotational speed target value of the motor; 
 a deceleration section calculation step in which the arithmetic controller calculates a deceleration section value of the motor, by multiplying the calculated rotational speed target value by the control cycle; 
 a temporary target position calculation step in which the arithmetic controller calculates a temporary target position, from a sum of the deceleration section and the stop start position; 
 a drive command calculation step in which the arithmetic controller calculates a drive command on the basis of a difference between a current position of the motor and the control target value, after determining the current position of the motor from the detection value detected by the detector using the temporary target position as a control target value; 
 an instruction step in which the arithmetic controller outputs the drive command to the motor; 
 the method further comprising a deceleration line calculation step in which the arithmetic controller calculates a new stop time until the motor stops at the target position from a time at which a predetermined control cycle elapses from the stop start position; and 
 in the rotational speed target value calculation step, the arithmetic controller calculates the rotational speed target value of the motor every time the control cycle elapses, on the basis of the rotational speed of the motor at a time at which the predetermined control cycle is elapsed from the stop start position, the new stop time, and the control cycle. 
 
     
     
       2. The motor stop control method according to  claim 1 , wherein the deceleration line is expressed by a quadratic function in which a slope of the deceleration line decreases as the deceleration line approaches the stop time. 
     
     
       3. The motor stop control method according to  claim 1 , wherein the predetermined angle is larger than a short brake stop angle at which a rotational speed of the motor is zero at the target position such that the arithmetic controller brakes the motor from a position before the target position using a short brake. 
     
     
       4. The motor stop control method according to  claim 1 , wherein the detector is a position sensor capable of detecting a position of the motor, and
 in the rotational speed calculation step, the arithmetic controller calculates the rotational speed on the basis of a detection signal of the position sensor. 
 
     
     
       5. A motor stop control apparatus comprising:
 an arithmetic controller that controls a motor; and 
 a detector that detects a rotational state of the motor, wherein 
 the arithmetic controller includes a control cycle which is a sampling interval used in detecting the rotational state of the motor at regular intervals and a stop start position at which a stop control is started from a position which is a predetermined angle before a target position at which the motor stops; and 
 the motor stop control apparatus further includes:
 a rotational speed calculator that calculates a rotational speed of the motor at the stop start position from a detection value detected by the detector; 
 a stop time calculator that calculates a stop lime until the rotational speed of the motor reaches zero from the stop start position on the basis of the rotational speed and the predetermined angle; 
 a rotational speed target value calculator that calculates a rotational speed target value of the motor every lime the control cycle elapses, from the rotational speed, the stop time, and a control cycle controlling the motor; 
 a deceleration section calculator that calculates a deceleration section value of the motor by multiplying the calculated rotational speed target value by the control cycle; 
 a temporary target position calculator that calculates a temporary target position from it sum of the deceleration section and the stop start position; 
 a drive command calculator that determines a current position of the motor from the detection value detected by the detector using the temporary target position as a control target value and calculates a drive command using a difference between the current position of the motor and the control target value; 
 an instructor that outputs the drive command to the motor; 
 the arithmetic controller calculates a new stop time until the motor stops at the target position from a time at which the control cycle elapses from the stop start position; and 
 the arithmetic controller calculates the rotational speed target value of the motor every time the control cycle elapses, on the basis of the rotational speed of the motor at a time at which a predetermined control cycle is elapsed from the stop start position, the new stop time, and the control cycle. 
 
 
     
     
       6. The motor stop control apparatus according to  claim 5 , wherein the predetermined angle is larger than a short brake stop angle at which a rotational speed of the motor is zero at the target position such that the arithmetic controller brakes the motor from a position before the target position using a short brake. 
     
     
       7. The motor stop control apparatus according to  claim 5 ,
 wherein the motor includes a rotatable shaft, 
 the shaft includes an output gear, 
 the detector includes a position sensor, 
 the position sensor detects an angle of the output gear, and 
 the rotational speed calculator calculates a rotational speed of the motor on the basis of the angle detected by the position sensor.